1. Field of the Invention
This invention relates to the prophylaxis and therapy of AIDS (acquired immune deficiency syndrome).
2. Background Information
The causative agent for AIDS is known to be a virus of the retrovirus family called HIV (human immunodeficiency virus). Infection with HIV does not, however, immediately give rise to overt symptoms of AIDS. The only indication of exposure to the virus may be the presence of antibodies thereto in the blood of an infected subject who is then described as xe2x80x9cHIV positive.xe2x80x9d The infection may lie dormant, giving rise to no obvious symptoms, and the incubation period prior to development of AIDS may vary from several months to several decades.
The reasons for the variable period between infection with the virus and breakdown of the immune system in an infected individual is poorly understood. Factors at present unknown may trigger proliferation of the virus with consequential disruption of the immune system. The victims of the disease are then subject to various infections and malignancies which, unchecked by the disabled immune system, lead to death.
Infection with HIV can, over time, weaken the immune system to the point where the infected individual has difficulty fighting off certain infections that are usually controlled by a healthy immune system. These infections are known as xe2x80x9copportunisticxe2x80x9d infections because they take the opportunity to infect individuals with weakened immune systems.
An HIV infected person receives a diagnosis of AIDS after developing one of the AIDS indicator illnesses as defined by the U.S. Centers for Disease Control. These conditions include
Candidiasis of bronchi, trachea, or lungs
Candidiasis, esophageal
Cervical cancer, invasive
Coccidioidomycosis, disseminated or extrapulmonary
Cryptococcosis, extrapulmonary
Cryptosporidiosis, chronic intestinal (greater than 1 month""s duration)
Cytomegalovirus disease (other than liver, spleen, or nodes)
Cytomegalovirus retinitis (with loss of vision)
Encephalopathy, HIV-related
Herpes simplex: chronic ulcer(s) (greater than 1 month""s duration); or bronchitis, pneumonitis, or esophagitis
Histoplasmosis, disseminiated or extrapulmonary
Isosporiasis, chronic intestinal (greater than 1 month""s duration)
Kaposi""s sarcoma
Lymphoma, Burkitt""s (or equivalent term)
Lymphoma, immunoblastic (or equivalent term)
Lymphoma, primary, of brain
Mycobacterium avium complex or M. kansasii, disseminated or extrapulmonary
Mycobacterium tuberculosis, any site (pulmonary or extrapulmonary)
Mycobacterium, other species or unidentified species, disseminated or extrapulmonary
Pneumocystis carinii pneumonia
Pneumonia, recurrent
Progressive multifocal leukoencephalopathy
Salmonella septicemia, recurrent
Toxoplasmosis of brain
Wasting syndrome due to HIV
An HIV positive person who has not had any serious illnesses can also receive an AIDS diagnosis on the basis of certain blood tests, in particular a CD4+ count.
Despite rapid growth of research into AIDS, no effective vaccine against it is yet available: it has been suggested that the genetic variability of the virus will in fact hamper the search for an effective vaccine.
The association between HIV infection and tuberculosis is well known. An early effect of HIV infection is the reactivation of previously dormant tubercule bacilli. The maintenance of resistance to mycobacteria is an active immunological process which is compromised by HIV infection. In dually infected persons, there is a high reactivation rate of dormant tubercule bacilli, and this reactivation usually occurs well before the appearance of other HIV/AIDS-related infections, which strongly suggests that an important effect of HIV infection is to destroy precisely those immune functions, presumably T-cell mediated, that maintain mycobacterial dormancy.
There is also evidence that where active tuberculosis is superimposed on HIV infection, there is a dramatic loss of CD4 T-cells which results in very rapid development of overt symptoms of AIDS. It appears in fact that immune mediators released in tuberculosis accelerate transactivation of the HIV provirus.
We have previously described the use of antigenic and/or immunoregulatory material derived from Mycobacterium vaccae in the treatment of tuberculosis (see, for example, British Patent No. 2,156,673 and U.S. Pat. No. 4,724,144).
We have now discovered that the same therapeutic agent not only delays development of AIDS in patients infected by HIV, but also is capable of causing regression, or even removal, of overt symptoms of AIDS even in patients where the disease is far advanced. These effects have been found in patients suffering also from tuberculosis, but are expected to occur also in patients who are suffering from HIV infection with or without AIDS and without associated tuberculosis.
The present invention accordingly provides a method for the prophylaxis or therapy of AIDS comprising administering to a subject who has been exposed to HIV infection or is HIV positive with or without overt symptoms of AIDS, killed cells of Mycobacterium vaccae in an amount sufficient to provoke an immune response effective to delay or prevent onset, or reduce the severity, of AIDS. The subject may or may not also show overt symptoms of tuberculosis.
The present invention also provides a method for reducing viral load in an HIV positive subject with or without AIDS. This object is achieved by administering to the subject killed cells of Mycobacterium vaccae in an amount effective to reduce HIV viral load.
The invention furthermore provides a method for stimulating an immune response in an HIV positive subject with or without AIDS. This object is achieved by administering to the subject killed cells of Mycobacterium vaccae in an amount effective to stimulate an immune response in said subject.
Means for achieving these and other objectives of the invention are set forth in the examples below, which are intended to describe the invention but not to limit it.
Therapeutic agents which may be used in the present invention comprise dead cells of M. vaccae, preferably cells which have been killed by autoclaving. The immunotherapeutic agent normally comprises more than 108 microorganisms per ml of diluent, and preferably from 108 to 1011 killed M. vaccae microorganisms per ml of diluent.
The diluent may be pyrogen-free saline for injection alone, or a borate buffer of pH 8.0. The diluent should be sterile. A suitable borate buffer is:
The preferred strain of M. vaccae is one denoted R877R isolated from mud samples from the Lango district of Central Uganda (J. L. Stanford and R. C. Paul, Ann. Soc. Belge Med, Trop. 1973, 53, 389). The strain is a stable rough variant and belongs to the aurum sub-species. It can be identified as belonging to M. vaccae by biochemical and antigenic criteria (R. Bonicke, S. E. Juhasz., Zentr albl. Bakteriol. Parasitenkd. Infection skr. Hyg. Abt. 1, Orig., 1964, 192, 133).
The strain denoted R877R has been deposited at the National Collection of Type Cultures (NCTC) Central Public Health Laboratory, Colindale Avenue, London NW9 5HT, United Kingdom on Feb. 13, 1984 under the number NCTC 11659.
For the preparation of an immunotherapeutic agent which may be used in the method of the present invention, the microorganism M. vaccae may be grown on a suitable solid medium. A modified Sauton""s liquid medium is preferred (S. V. Boyden and E. Sorkin, J. Immunol, 1955, 75, 15) solidified with agar.
Preferably the solid medium contains 1.3% agar. The medium inoculated with the microorganisms is incubated aerobically to enable growth of the microorganisms to take place, generally at 32xc2x0 C. for 10 days. The organisms are harvested, then weighed and suspended in a diluent. The diluent may be unbuffered saline but is preferably borate-buffered and contains a surfactant such as Tween 80 as described above. The suspension is diluted to give 100 mg of microorganism/ml. For further dilution, borate-buffered saline is preferably used so that the suspension contains 10 mg wet weight of microorganisms/ml of diluent. The suspension may then be dispensed into 5 ml multidose vials. Although the microorganisms in the vials may be killed using irradiation, e.g., from 60Cobalt at a dose of 2.5 megarads, or by any other means, for example, chemically, it is preferred to kill the microorganisms by autoclaving, for example, at 10 psi for 10 minutes (115xc2x0-125xc2x0). It has been discovered that autoclaving yields a more effective preparation than irradiation.
The immunotherapeutic agent is in general administered by injection in a volume in the range of 0.1-0.2 ml, preferably 0.1 ml, given intradermally. A single dosage will generally contain from 107 to 1010 killed M. vaccae microorganisms. It is preferred to administer to patients a single dose containing 108 to 109 killed M. vaccae. However, the dose may be repeated depending on the condition of the patient.
Although the immunotherapeutic agent will generally be administered by intradermal injection, other routes, e.g., oral administration, can also be used.
For 20 to 50% of African patients with HIV infection, tuberculosis is the first symptom in development of AIDS. Tuberculosis infection is associated with significant production of interleukin 6 (IL6) and tumour necrosis factor (TNF). There is evidence to show that the addition of TNF and IL6 to HIV-infected T cells in vitro leads to increased multiplication of the virus. The TNF release associated with tuberculosis infection in an HIV-positive subject may precipitate proliferation of the HIV with consequential disruption of the function of T4 cells in the immune system and production of immunodeficiency.
It is believed that the prevention of tuberculosis or, more specifically, the inhibition of TNF, and IL6 associated (Koch) responses, will have a delaying effect on precipitation of the AIDS syndrome. The agents of the invention are believed to exert an immunomodulatory effect on pre-existent cell mediated necrotising responses, changing them to a non-nectrotising form of response and that this is due to decreased production of, or a change in function of, IL6 and TNF. It is also believed that protective immunity against both tuberculosis and leprosy are enhanced.
Among a group of patients being treated for tuberculosis were seventeen who were seropositive by the Wellcome ELISA for HIV1. All the patients were prescribed streptomycin, isoniazid, rifampicin and pyrazinamide for their tuberculosis. Therapy was abbreviated and did not last longer than three months in any case. Eight of the seventeen patients received the therapeutic agent of the present invention and nine received placebo (saline). At follow-up about one year later, only three of the patients who had received the anti-tuberculosis drugs only had survived and all three of these had advanced tuberculosis. Seven of the eight patients treated with the therapeutic agent of the present invention had become sputum smear negative for acid fast bacilli (i.e., tubercule bacilli) and the general improvement in their condition was similar to that in tuberculosis patients who were not HIV positive. Five of the eight patients had generalized lymphadenopathy at the time of diagnosis. This had resolved at the time of follow-up. The two patients who were re-tested serologically at the follow-up were found to be negative for HIV1.
It may be advantageous and is within the scope of the invention to use more than one strain of M. vaccae, and/or include in the therapeutic agent other mycobacterial antigens. Tuberculin may also be included.
The therapeutic agent may also contain BCG (Bacillus Calmette-Guerin) vaccine, in particular the freeze-dried form of the vaccine, to promote its effect.
The therapeutic agent can contain further ingredients such as adjuvants, preservatives, stabilizers, etc. It may be supplied in sterile injectable liquid form or in sterile freeze-dried form which is reconstituted prior to use.
M. vaccae may be used as such or as an extract or fractionated portion of the organism to prepare therapeutic agents according to the invention.